refactor ValidationFormatter for compatibility and better arch

Validation now happens directly in the ValidationFormatter
and no longer in the ValuesGroupValidator (which is removed)

The ViolationMapper is removed as Violations are now directly set
in the ValidationFormatter

Last this fixes compatibility for Symfony 2.4 and up
fix FieldTypeValidatorExtension wrong options config
bug #27 refactor ValidationFormatter for compatibility and better arch (sstok)

This PR was merged into the master branch.

Discussion
----------

|Q            |A  |
|---          |---|
|Bug Fix?     |yes|
|New Feature? |no |
|BC Breaks?   |no |
|Deprecations?|no |
|Fixed Tickets|#24|
|License      |MIT|

Commits
-------

e650a707d36c387add66539be7d198b7d386f0ac refactor ValidationFormatter for compatibility and better arch
4f75b677d709f6b7ffd36d9599e06259ae142bf1 fix FieldTypeValidatorExtension wrong options config